The negative pion (-) is an unstable particle with an average lifetime of 2.60 x 10-8 s

Question:

The negative pion (π-) is an unstable particle with an average lifetime of 2.60 x 10-8 s (measured in the rest frame of the pion).
(a) If the pion is made to travel at very high speed relative to a laboratory, its average lifetime is measured in the laboratory to be 4.20 x 10-7s. Calculate the speed of the pion expressed as a fraction of c.
(b) What distance, measured in the laboratory, does the pion travel during its average lifetime?